1. Field of the Invention
The present invention generally relates to a collision detection apparatus, a collision detection method and the robot and vacuum cleaner using the same.
2. Description of Related Art
A mobile intelligent robot, from the cradle phase to fully developed phase thereof, has closely bound the technologies, such as mechanism design, electrical control design, kinetic control theory and sensors.
In order to make a mobile intelligent robot, the robot needs to know the relative position between the surrounding obstructions, thus, collision detection is an important topic. In addition, collision detection also serves as a guard line for a robot movements in an environment with obstructions. That is to say, a robot would not get damaged or hurt any object in the environment during the movement thereof, especially human body, by all means.
The existing collision detection method is roughly classified into two schemes: to calculate the object position by means of video/audio data, which requires numerous computations to detect the obstructing object position by using a collision detecting system. The advantage and the disadvantage of each the scheme are described in the following.
With the contact-type collision detection method, an anti-collision retraction lever is used to detect whether an object is touched so as to judge a collision occurrence. In more detail, one or more anti-collision retraction levers are disposed on the periphery of a robot's main body and the anti-collision retraction lever is linked with a linkage mechanism where a light-blocking proximity sensor or a touch sensor is connected thereto. Once a collision occurs, the articulator-like linkage would rock, and the light-blocking proximity sensor or the touch sensor would sense the rocking movement to make the robot aware of the collision. However, the disadvantage of the detection method is that it fails to detect the extent of collision, for example, the amount of collision force, although it detects the collision occurrence. Beside, restricted by the structure inherence of the anti-collision retraction lever and the internal levers thereof, the method is unlikely to achieve the effects of a soft collision and automatic shock-absorption due to a limited resolution, when the anti-collision retraction lever of a robot encounters a collision, the method fails to accurately identify the orientation of the collision point so that the robot is unable to correctly determine a collision-free route. Furthermore, a risk of false action exists with the robot, for example, for a detection apparatus which is designed to function only when the anti-collision retraction lever gets a translation movement and the linkage mechanism rocks caused by a collision, if only an edge of the anti-collision retraction lever were collided, the linkage mechanism may not rock and the detection apparatus would be silent in response to a real collision; moreover, such a contact detection scheme may damage or hurt an obstructing object in a mobile environment, especially a human body.
With the collision detection method using an optical sensor, if an obstructing object were a blackbody incapable of reflecting light, the detection does not function. In other words, the optical collision detection method has a certain requirement on the surface of an obstructing object. On the other hand, if an obstructing object reflects light somewhere, rather than at the robot itself, the detection does not function as well. In other words, the detection angle with the optical collision detection method is limited.
With the collision detection method using an acoustic sensor, a huge computation is needed, which makes the method hard to be used for fast moving circumstance while keeping away from any obstructing object. Furthermore, the method also likely causes a false judgment of a route with a specific angle or a slope.
With the collision detection method using an impedance sensor, a circuit of driving the wheels of the robot keeps monitoring the voltage/current variations. If the driving motor turns with more effect, a decreased voltage and an increased current would be monitored, which indicates the robot encounters an obstructing object. But the same detection result can be given if the robot walks on lawn, carpet or hill, which causes a false judgment as well.
With the collision detection method using an magnetic sensor, a great number of magnetic bars is required to be disposed around in the working environment for the first time use, which is a troublesome task and the method is suitable for a factory with simple establishments only. In addition, the method is not able to detect a moving obstructing object that temporarily enters the environment; not to mention, a moving obstructing object such as a human or animal that dislikes to be adhered by a magnetic sticker.
With the collision detection method using an electronic map, although the position information of the obstructing objects provided by the electronic map can be used to avoid obstructions, but prior to completely creating the electronic map, the above-mentioned methods are still needed for initially avoiding obstructions. The error of the sensing system with the method would be increased all the time and needs to be always calibrated. Moreover, the method is unable to detect a moving obstructing object.